The train from Nouadhibou to Zouerat is the longest train in the world. The iron ore train carry thousands of tons of crusehed rock in a chain of wagons up to three kilometres long. Their schecules and frequencies depend partly on the speed of the extraction at the mines, and even in the past, attacks by Polisario guerillas from over the border in Western Sahara.

There are 3 or 4 diesel-electric General Motors 3300V locomotives at the head of the train and about 200 cars each carrying up to 84 tons of iron ore, and a variable number of service cars. The total traffic averages 16.6 billion tons per year.

Travelers' cars are also occasionally transported by train; these services are managed by an SNIM subsidiary, the ATTM Society (Société d'assainissement, de travaux, de transport et de maintenance). Passenger cars are sometimes attached, but more often passengers simply ride atop the ore cars.